The present invention relates to pressure transducers, and more particularly to an improved wet-to-wet differential pressure transducer.
There are many types of pressure transducers for which there are many well known uses. One particular type of transducer is that conventionally characterized as being wet-to-wet and which can be used to measure the differential pressure between two fluid or gaseous substances for example. Wet-to-wet differential transducers are used in automotive, medical and aerospace applications.
Piezoresistive sensor structures are widely used in pressure or force measuring. Generally, the prior art is replete with a number of patents which describe various configurations and methods of fabricating piezoresistive pressure sensing devices. Typically, a piezoresistive device includes a bridge pattern of piezoresistive resistors which are formed on or within one side of a relatively thin deflecting member. The deflecting member, which may be fabricated from silicon, (as well as the resistors) deflects upon application of a pressure thereto which causes the piezoresistors to vary their magnitude as is well known. If a pressure P, is applied to one face of the deflecting member and a pressure P2 is applied to the other face of the deflecting member, the resulting deflection will be determined by the difference in pressure P1,-P2. Thus, differential pressure measurements can be accomplished using a differential transducer, which provides an output, which is the difference between two pressures. Examples of both absolute and differential piezoresistive bridge pressure transducers are illustrated in commonly assigned U.S. Pat. No. 4,222,227, entitled xe2x80x9cMEDIA COMPATIBLE PRESSURE TRANSDUCERxe2x80x9d, the entire disclosure of which is hereby incorporated by reference.
If oil-filled cavities are used in conjunction with media-isolation diaphragms, it is desirable to minimize the quantity of oil included in the oil-filled pressure communicating cavity to improve sensor performance. It is further desirable to miniaturize the pressure-sensing device as size and weight is often design considerations in many applications.
It is the object of the present invention to provide a miniaturized and hence improved wet-to-wet differential pressure-sensing device.
A pressure sensing device including: a housing including a first port and a second port; a pressure transducer secured within the housing between the first and second ports, said sensor having one face capable of being exposed to a pressure P1 and the other face capable of being exposed to a pressure P2 said sensors having overpressure stops in each direction, i.e. P1 and P2; a first isolation diaphragm, secured within the housing between the first port and the sensor; a second isolation diaphragm secured within the housing between the second port and the sensor, said isolation diaphragms serving to insure that the pressure media from the first and second ports do not directly touch the sensor; a first filling tube for introducing a fluid material into a first cavity located between the first isolation diaphragm and the sensor; and, a second filling tube for introducing fluid material into a second cavity located between the second isolation diaphragm and the sensor; wherein the first and second filling tubes are fastened to a side wall of the housing being interposed between the first and second ports, and each tube separately intersecting holes formed at right angles to the tubes, one hole going into the first cavity and connecting to the first tube and a second hole accessing the second cavity connected to the second tube.